Safety means for motors



Sept. 5, 1939. ,P. D. CORNELIUS 2,172,240

SAFETY MEANS FOR MOTORS y Filed Jan. 27. 1937 3 Sheets sheet 1 ,l U muy' 142. Q 3,316 l Ewwzw' Sept. 5, 1939. P. D. CORNELIUS 2,172,240

l SAFETY MEANS FOR MOTORS Filed aan., 2'?, 1937 s sheets-sheet 2 Sept. 5, 1939.

` P. D. CORNELIUS SAFETY MEANSFOR MoToRs Filed Jan. 27, 193'? nimm 3 Sheets-Sheet 3 Patented Sept. 5, 1939 SAF ETY IW'EANS` F OR MOTORS Paulr D. Cornelius, Tulsa, Okla., assgnor` to Sullivan Machinery Massachusetts Company, a corporation of Application January 27, 1937, Serial No. 122,622

21 Claims.

My invention relates to expansible chamberl motors, and more particularly to expansible chamber Vmotors of a type especially adapted for pumping and similar uses. From one aspect, my invention relates to protective devices for such motors.

There is available in some oil fields a substantial quantity of oil in Wells whose subterranean pressure is inadequate to cause the oil to flow naturally. Pumping motors therefore have to be used for the purpose of raising the fluid to ground level. EXpansible chamber, single-acting pumping motors have been found very satisfactory for this purpose, their pistons operating, through suitable pump rod Ilines, pumps arranged in the oil wells. Such pumping motors are frequently arranged in groups near a central source of operating pressure fluid supply, and individual pumps are not generally attended by runners.

' Accordingly, it is quite important that the pumping motors be made as nearly completely automatic and self-protecting as possible,-

'Ihe pump rod lines by which such pumping motors are connected with the pumps in the wells are often some thousands of feet in length. The described method of pumping makes the pump rod lines last-much longer than where they are operated, for example, by a walking beam, but

pump rod failures do occur at times, and when .such a failure occurs it is important to minimize the damage. If the motor piston is allowed to accelerate throughout the remainder of its working stroke, unchecked bys-the normal weight of its load, and then suddenly brought to rest, it is '.possiblefor serious damage to occur` to the. portion ofthe pump rods which remain connected to the pump piston, and also to the motor, and accordingly it is desirable to cushion the upward stroke of the pumping motor piston as soon as fpossible after the breakage occurs. It is also important that the pump motor piston shall not be retarded in its normal working cycle, but that the increase in cushioning, which sthe mode of protection upon which I. particularly rely, take place automatically when the pump motor piston travels at an excessively high rate. While it is possible to arrange my device in any desired relation to the cycle of the pumping motor, provided there will be time for adequate cushioning before the end of the stroke, following a rupture of the pump rod line, the fact that -there is perhaps a greater stressing of the rods during the earlier portions of the Working strokes of the motor makes it possible -to providefor the automatic control primarily during-'the earlyv portions of the pumping strokes and still provide a very reasonable range of safety.

In a preferred embodiment of the invention, I associate with a pumping or similar motor means for by-passing pressure from the working side of the motor piston to the other side thereof, and control that bypassing means by means operating concurrently with the pumping motor piston and desirably under the control of the fluid distribution to the pump, such that excessive piston speeds will cause bypassing, whereas normal piston speeds will prevent bypassing. Desirably, this result is accomplished by regulating the rate of movement of a valve controlling a bypass so that the same will close the bypass, if the piston movement is normal, before the moving motor piston attains a position in which fluid would have access to the lower end of the bypass, said valve-closing means, however, being ineffective to effect valve closure before bypassing takes place if the piston speed is materially augmented above normal. Very desirably, the bypass control means may be operated so as to return the bypass controlling valve to its completely inoperative position should bypassing occur,

It is an object of my invention to provide an improved pumping or similar motor having improved protective devices associated therewith. It is another object of my invention to provide an improved pumping motor having an improved fluid-actuated protective device associated therewith. It is a further object of my invention to provide an improved pumping motor having an improved automatically controlled bypassing device associated therewith for checking the piston movement of said motor in the event that excessive piston speeds develop. It is still another object of my invention to provide an improved automatic bypass-controlling device for a pumping motor, or for similar purposes, in whichy a bypass-controlling valve traverses a working cycle as the pumping or other motor traverses its own cycle, certain portions of the control-device cycle being at a different rate from the corresponding portions of the motor cycle. Other objects and advantages of my invention will hereinafter more fully appear.

In the accompanying drawings, in which for purposes of illustration I have shown one embodiment which my invention may assume in practice- Fig. 1 isa View, in side elevation, of a pumping motor equipped in accordance with the illustrative embodiment of the invention.

Fig. 2 is a developed section through the lower end of the pumping motor cylinder and through the distributing valve therefor.

Fig. 3 is a section approximately on the line 3-3 of Fig. 2, with parts shown in a different position.

Figs. 4, 5 and 6 are views, partially in section, through the pumping cylinder and the automatic bypass-controlling device associated therewith, showing respectively the position of the parts early in a normal pumping stroke, somewhat later in a normal pumping stroke, and at the same time in a stroke where the piston moves with abnormal speed due to some such derangement as a broken pump rod line.

Referring to the drawings, and particularly to Fig. 1, it will be noted that a suitable support', of which a fragment is shown at 2, carries a motor, generally designated 3. Said motor may be of widely differing constructions, and herein there is shown, for illustration, a motor which is the invention of one Wade H. Wineman, and which forms a portion of the subject matter of his application Serial No. 102,987, led September 28, 1936, and owned by my assignee. This motor includes an upper cylinder head member 4', a lower cylinder head and valve chest member 5, and an elongated cylinder member 6. The cylinder member 6 is herein made up of two parts, the lower one designated 6a and the upper one designated 6b, the part 6a being more properly a motor cylinder and the part 6b essentially a dash-pot cylinder. A bore of uniform diameter, and designated 1, extends throughout the full length of the cylinder 6. A piston 8 is reciprocable within the bore 1 and has connected to it a piston rod 9 which is connected in any suitable manner through a pump rod line to a pumping motor arranged in a well. The piston 8 is single-acting, and pressure admitted beneath the same raises it, while its downward movements are caused by its own weight and that of the connected pump rod line and pump parts when a reduction in the pressure beneath the piston occurs. The downward movement of the piston is suitably retarded by providing a constant back pressure of an appropriate amount against which the non-working strokes of the piston 8l lare made. Tie rods l0- connect the two cylinder heads 4 and 5 and clamp them to the opposite ends of the cylinder 6.

The lower cylinder head 5 supports the distribution means for the motor. A fluid supply space i3 has fluid supplied to it through a supply connection I4, as shown in Fig. 1. An eX- haust space I5, which has an exhaust connection I6, as shown in Fig. 1, is adapted to receive the exhausting fluid from the pump motor cylinder and to deliver it against a back pressure, as above described. Operating fluid may desirably be supplied at a pressure of perhaps 200 or 300 pounds per square inch, the pressure depending, of course, upon the depth of the well, the size of the pump, and the height through which the oil may have to be raised. The back pressure may advantageously be from fty to a hundred pounds, depending also upon the operating conditions. The back pressure simply needs to be made high enough to control in a proper manner the downward movement of the piston 8 and its connected parts, without being so high as unduly to retard the downward movement of these parts. A generally annular space I1, arranged between the spaces i3 and I5, is connected by a suitable port I8 to the lower end of the motor cylinder 1. A septum I9 separates the supply space I3 from the cylinder connected space I1, while the exhaust space I5 is separated from the cylinder connected space I1 by another septum 20. A sleeve 2| provides a valve chamber and is mounted in vertical position in a series of bores of progressively decreasing size, numbered respectively 22, 23, 24, 25 and 26, and has shoulders, unmarked with reference characters, cooperating with the annular surfaces provided at the ends of certain of said stepped bores. A head 28 closes the lower end of the bore 26 and has a reduced portion 29 fitting and closing the lower end of a bore 30 which extends for approximately the lower three-fourths of the length of the sleeve 2|. A larger bore 3| communicates with the bore 3U at theV upper end of the member 2|. The bores 30` and 3|' together form a valve chest 32. An upper head 33, held by a series of side rods 34, clamps the member 2| in position, while suitable screws clamp the lower head 28 in position. It may be noted that the valve chest member 2| is not a close fit for the surrounding wall of the'lower head member, and accordingly, since a passage 23a is provided in the lower head member 28 to connect the periphery of the reduced portion 29 thereof with the central upper face thereof, there is communication between the Vexhaust space I5 and the lower end. of the bore 30, so that the lower end of said bore 30 is continuously under motor back pressure. The sleeve member 2| is provided with radially extending ports 36 connecting the bore 30 with the space I3, while ports 31 connect the space I1 with the bore 30, and ports 38 connect the space I5 with the bore 30.

A valve 4D, desirably constructed of aluminum or other light metal in order to speed up its movements and reduce the forces necessary to move it, is reciprocable in the bores 30, 3|, and has a large head 4I fitting the bore 3| and two smaller heads 42V and 43, each fitting the bore 39. Suitable packing means 44 are provided for each head, and the` upper and lower heads are separated from the middle head by annular grooves, the lower annular groove designated F and operative to connect the space |1 alternatively with the supply space I3 and with the exhaust space I5. Thel valve member carries centrally thereof and at its upper end a spring pressed valve 45, which normally projects slightly above the top of the valve member and is normally held in its maximum degree of permitted projection by a spring 46. The strength of this spring issuch as to maintain the valve 45 seated despite the action of fluid pressure upon its extremity, when said valve is seated, but the spring yields, none the lessto prevent jamming of the parts as the valve, member 40 moves upwardly against its seat. A stationary guide rod 48, and a bore 41 in the Valve, prevent rotation of the valve 46 during its reciprocation. The upper end of the valve is provided with a small block of steel or other hard material, at 49, and this is adapted to engage the stem of a valve 56 carried within the upper head 33. The top of the valve chest 32 is connectible with the cylinder bore at two widely spaced points in the latter. A bushing 52, having a passage 53 therein, is arranged centrally of the valve chest in the head 33 of the latter, and, through a suitable tubing arrangement 54, is connected withY a point 55 in the cylinder bore 1, saidr point so located as to be un'covered by the upperA end of the downwardly moving piston 8 shortly before thel latter reaches its lowermost position. Theilower end of bushing 52 provides a seat 45 for the valve 45 when the valve 48 is in its upper position. Another connection leads from the cylinder bore 1 at a point 56 therein, this point so located that the lower end of the piston 8 passes above it only substantially as the piston 8 completes its desired upward travel. The .point 56 is connected through suitable tubing arrangements, generally designated 51, with a space 58 above the ported check valve element 58 heretofore mentioned. Said check valve element has passages 59 therein which enable fluid to flow through said valve from end to end thereof when said valve is unseated. The valve 58 is unseated, of course, when Ithe block 49 engages the valve stem 6I and a passage is then opened, through the annularspace 62 surrounding the stem 6l and through the passages 59 and through the connection 51, between the chamber 3l an the cylinder bore.

l The bore of the cylinder section 6b may desirably be vented to atmosphere through a mechanism including an automatic vent check device, generally designated 10. The structure of this device is shown in my assignees copending application Serial No. 102,987, and it will suce to say that this device permits breathing of the motor cylinder during normal motor operation with very small changes in pressure within the cylinder. When, however, air tends to be displaced from the motor cylinder at a rate in excess of .a certain predetermined one, the vent check device closes all except a relatively small port between the top of the pump motor cylinder and the atmosphere, and accordingly the uid is largely trapped within the top of the pump motor cylinder and a cushion pressure more quickly built up.

The mode of operation of the structure so far described will be clear. To trace a cycle through,

assume that the distributing valve is in the position shown in Fig. 2. In this position of the distributing valve, the piston 8 is still moving downwardly. In a short time, however, its upper end will pass below the point of connection, 55, with the cylinder bore, and thereupon, through the connection 54 and through the upper end of the cylinder, the cylinder pressure which is acting, in the positio-n of Fig. 2, on the upper end of the piston portion 4I and holding the valve in the lower position in which itis shown, will be vented to atmosphere; and accordingly the constant pressure acting on the lower end of the piston portion 43 will move the distributing valve up to the position shown in Fig. 3. The pressure previously acting on 4l in Fig. 2 was, of course, only that which was concurrently acting on the bottom of 43, but since 4l is larger than 43 the valve was held in the position shown, both by the preponderance of pressure on its upper end and by its own weight. As soon as the parts attain the position shown in Fig. 3, motive uid will pass from the space I3 through the groove F into the space l1, and thereby into the lower end of the cylinder, beneath the piston 8, and the piston 8 will begin to move up. As it moves upwardly, its lower end will first move above the point 55, and live fluid from the cylinder bore will pass through the passage 54 down to the top end of the valve 45, but will not be able to attain entrance into the top end of the valve chest because the valve will be seated. 'Ihe piston 8 will accordingly continue its upward movement unt1l its ylower end passes above the connection polnt 56, and then pressure will ilow through the con'-` 'nection 51, through the passages 59 in the thenopened valve 58, and through the annular space 62, and act on the larger, upper area of the distributing valve 48, and start the latter down to cylinder-venting position; and valve throw, which will be commenced by pressure through the connection 51, will be completed by pressure through the connection 54 and passage 53.

As soon as the valve again attains the position shown yin Fig. 2, the motor piston 8 will start downward, because the pressure below it will reduce substantially to motor back pressure, an amount inadequate to support the weight of the piston 8, piston rod 9, etc. When the piston 8 moves below the connection point 56, the pressure within the line 51 will be vented, but the pressure above the distributing valve will be retained because the Valve will still prevent the escape of any pressure through the line 51. Accordingly, the piston 8 will continue to move downward until its upper end passes below the connection point 55, at which time the pressure acting on the upper end of the distributing valve will be vented to atmosphere through the connection 53, 54 and the upper end of the cylinder bore, and the valve will again move to the position shown in Fig. 3, so that a new up stroke of the motor piston 8 will take place. Such mode of operation will continue so long as motive iluid is supplied to the pumping motor, barring derangement thereof or loss of load thereby.

As a preliminary to describing the improved automatic control means, it may be pointed out that the working strokes of the motor piston 8 include an initial period of relatively rapid acceleration and thereafter a sustained period of relatively constant velocity, acceleration occurring rapidly as the pump rod line stretches.

Now, taking up the automatic protective device for the motor, it will be observed that the upper end of the cylinder portion 6b has a connection 80 leading thereto; and a connection 8l opens into the motor cylinder portion 6a at any suitable place therealong-desirably a position sufciently far up so that the upwardly moving motor piston will reach it and pass beyond it only when moving at the nearly constant rate which prevails during most of its working travel. The connection 8| leads into a valve casing 82 which has a top opening 83 connected by a pipe 84 with a check valve 86 opening toward the connection 88, which is operatively connected with the check valve 86 at the cylinder end of the latter. The casing 82 has a spa-ce 88 therein in constant communication with the cylinder bore 1 through the connection 8l, and an internal bore 89 in which a valve 98 is reciprocable, the bore 89 being connected with the opening 83 at its upper end, and through radial passage 9| with the space 88. A spring 92- extends between the upper end of the bore 89 and a surface 93 inside the valve 90. It will be noted that the valve 98 has a substantial distance to travel from its lowermost position in the bore 89 to a position in which its upper end will overrun the ports 9|. 'Ihe lower end of the bore 89 is closed by a plug 95 through which, and a conduit 96, fluid flow to and from the lower end of the bore 89 is possible. In order to permit a desirably slow supply of fluid to the lower end of the bore 89, the connection 96 has a double connection with a connection 91 which leads to the cylinder bore 1 at a point near the lower end of the latter. One branch of the double connection, numbered 98, has a check valve 99 therein which precludes flow from 91 towards 96 but enables rapid flow in the opposite direction. The

otheri branch of the double connection, |08, has a manually adjustable valve |01 therein which mayA be manually adjusted to provide a controlledY slow rate of live fluid flow from the bore of the cylinder: tothe connection 96;

The mode of operation of the complete structure will now be understood. It will be appreciated that every time the distributing valve 40 admits pressure to the motor cylinder bore 1 and the piston 8V is above the point of communication of the connection 91 with. the cylinder bore, motive fluid will flow past the valve |0|, through the connection 99 and the connection 96 and plug 95, beneath the valve element 90, and start the latter to moving upwardly. Because of the controlled rate of uid supply past the valve |0| and the4 resistance imposed by the spring 92, a certain amount of time will elapse between the first supply of fluid beneath the valve 98 and the attainment of the valve 98 to a position to close the ports 9|. Therefore, if the motor piston 8 moves fast enough to get above the connection 8| before the valve 90Vgets above the passages 9|,

uid from beneath the piston 8 will pass through the connection 8|, chamber 88, ports9l, bore 89, connection 84, check valve86, and connection 80, to the upper end of the pumping cylinder, and begin immediately to cushion the upward movement of the latter. It, however, the pumping motor piston 8 does not move rapidly enough to get above the connection 8| before the valve 98 closes the ports 9|, the valve 90 will prevent bypassing of fluid from beneath to above the piston 8 when the piston ultimately passes above the connection 8 Now, by regulating the rate of admission of fluid beneath the valve 98 in such a manner that the same will reach and close the ports 9| slightly before the lower end of the upwardly moving :.piston 8, if the latter is moving normally, gets to the lower edge of the connectionV 8|, bypassing will be prevented and the motor piston will operate in a normal manner throughout its complete cycle. It will be understood, moreover, that 1. when the motor piston upon its downward movements gets below the point of communication with the cylinder bore of the. connection 8|, the pressure within said connectionA will simply be vented to atmosphere. If during the starting of s thepump piston and bringing it up to speed, the

rod line breaks, the piston 8 will jump ahead, so to speak, and uncover the pointV of communication of passage 8| with the bore before valve 90 closes passages 9|, and so fluid will pass through connection 88 and cushion the upwardly moving, relatively unloaded` piston. As valve 98 will have similar pressures on its opposite ends, its upward movement will be checked and the spring 92 will force it down to its bottom position.

Desirably this devicel may be used with equipment for locking the distributing valve in exhaust position, as described in my assigneesf application Serial No. 102,989, iiled September 28, 1936, now Patent No. 2,156,326, granted May 2, 1939, so as to insure complete stopping of the motor.

It. will be evident that I have provided an` improved safety device of the character described which is simple, certain in operation, and highly effective under the conditions for which it is designed, and that it is adapted to certainty of functioning because it goes through cyclic movements continuously while the motor which it is protecting operates'.

While there is inA this application specifically described one form which this invention may assume in practice, it will be understood that this form: o-fthe same is shown forpurposes of illustration, and that the invention may be modified and embodied in various other forms without departingfrom its spirit or the scope of the appendedv claims.

What I claim as new and desire to secure by Letters' Patent is:

1f. In combination, an expansible chamber motor having a cylinder containing a reciprocatingpiston', meansl including a bypass for admitting uid at working pressure from the working to the non-Working end of said cylinder automatically, early in the working stroke of said motor, in the event said motor loses itslload, and` means responsive to cylinder pressures for precl'uding such admission during normal motor' operation.

2. In combination, an expansible chamber motor having av cylinder containing a reciproeatingv piston, aY bypass connecting. spaces at` opposite: sides of. said,` piston during the working stroke thereof, and a. valve controlling said bypass' andY traversing: a cycle4 of movement concurrently with said piston.

3. In combination, an expansible chamber motor having relatively reciprocablei cylinder and piston elements,` a bypass extending between spaces inl said cylinder separated by said' piston, a. valve controlling said bypass,y and means for causingv said: valve to,` traverse` a cycle of movement occluding saidbypass during the latterportions of each normal working stroke' of said motor;

4. In combination, an expansible chamber motor'having relatively reciprocabl'e cylinder and piston` elements, distributingcvalve means for. ad-

mitting and venting pressure relative to one end of said motor cylinder, means connecting the other-endl of said' motor cylinder with a point in the` first end to whichV working pressure attains only after-ay predetermined portion of the working; stroke,V and means controlling said connecting' means includingl a valve yieldingly pressed towards openposition and subjected toY working pressure underthe control of said distributing valve for said passage automatically moved in a .f-

direction to preclude delivery of fluid through said passage upon each admission of fluid to said motor...

6..In combination,A a motor including a cylinder,,` distributing valvev mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically delivering fluid from the working end of said motor to its opposite end in the` event of excessive piston speeds, including means forming a passage for the transmission of such fluid, a controlling valve for. said passage automatically movedv in a direction toA preclude delivery of fluid through said passage upon each. admission offluid to said' motor, and means for controlling the rate of movement.. of said valve;

'7; Inv combination, a motor including a. cylinder, distributing valve mechanism,H a piston, and uid 'supply and exhaust means for said motor, and; means forV automatically deliveringv fluid from the Working end of said motor to its opposite end in the event of `excessive piston speeds including means forming a passage for the transmission of such fluid, a controlling valve for said passage automatically moved in a direction to preclude delivery of fluid through said passage upon each admission of fluid to said motor, and means for controlling the rate of movement of said valve to provide a retarded rate of movement thereof in a p-assage-interrupting direction and a rapid opposite movement.

8. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said moto-r piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a Working direction and having its other end opening into the opposite end of said cylinder, and a controlling valve for precluding flow of cushioning fluid through said passage during normal operation of said motor.

9. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of `cushioning fluid from the Working end of said motor to the oposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a Working direction and having its other end opening into the opposite end of said cylinder, and a controlling valve for precluding flow of cushioning fluid through said passage during normal operation of said motor and means for admitting operating fluid to the same during admission to said motor cylinder by said distributing valve mechanism.

10. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a Working direction and.

having its other end opening into the opposite end of said cylinder, and a controlling valve for said passage having means for admitting operating fluid to move the same upon admission to said motor cylinder, and means for opposing its movements by such fluid.

11. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a Working direction and Vhaving its other end opening into the opposite end of said cylinder, and a controlling valve for said passage having means for admitting operating fluid to move the same upon admission to said motor cylinder and for venting such iluid upon exhaust of fluid from said motor cylinder.

12. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered b-y the motor piston after a predetermined movement of the latter in a working direction and having itsA cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a Working direction and having its other end opening into the oppositeend of said cylinder, and a controlling valve for said passage having means for admitting operating fluid to move the same upon admission to said motor cylinder and for venting such fluid upon exhaust of fluid from said motor cylinder, said venting means having a check valve limiting flow to a direction towards said motor cylinder.

Y 14. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding o-f said motor piston including a passage having one end thereof uncovered by the motor piston after a predetermined movement of the latter in a working direction and having its other end opening into the opposite end of said cylinder, and a controlling valve for said passage having means for admitting operating fluid to move the same upon admission to said motor cylinder and for venting such fluid upon exhaust of fluid from said motor cylinder, said admitting means having adjusting means for controlling the rate of flow therethrough and said venting means having a check valve limiting flow to a direction towards said motor cylinder.

15. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for cushioning movement of said piston in the event of overspeeding of the latter including a bypass provided with means for permitting passage of fluid from the Working end of the cylinder to the opposite end thereof but precluding reverse flow, and an automatic controlling valve governed b-y motor cylinder pressure for closing said by-pass to Working fluid during normal motor operation.

16. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fluid supply and exhaust means for said motor, and means for cushioning movement of said piston in the event of overspeeding of the latter including a bypassl provided with means for permitting passage of fluid from the working end of the cylinder to the opposite end thereof but precluding reverse flow, and an automatic controlling valve governed by motor `cylinder pressure for closing said by-pass to Working fluid during normal motor operation, said controlling valve moving in a closing direction during Working strokes of said motor piston and oppositely during the latter part of the intermediate strokes of said motor piston.

17. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and uid supply and exhaust means for said motor, and means for cushioning movement of said piston in the event of overspeeding of the latter including a by-pass provided With means for permitting passage of fluid from the `Working end of the cylinder to the opposite end thereof but precluding reverse now, a controlling valve governed by cylinder pressure closing said by-pass to working fluid-during normal motor operation, yielding means opposing closure of said controlling valve, and means admitting cylinder pressure to aid said yielding means in preventing closure of said controlling valve during excessive piston speeds.

18. In combination, a motor including a cylinder, distributing valve mechanism, a piston, and fiuid supply and exhaust means for said motor, and means for automatically effecting a supply of cushioning fluid from the Working end of said motor to the opposite end thereof in the event of overspeeding of said motor piston including a passage having one end thereof uncovered bythe motor piston after a predetermined movement of the vlatter in a working direction and having its other end opening into the opposite end of said cylinder, and a controlling valve vfor precluding ow of cushioning fluid through said passage during normal operation of said motor and controlled by pressure in said cylinder.

19. In combination, a motor including a cylinder, distributing Valve mechanism, Va piston,-and fluid supply and exhaust means for said motor, a bypass for delivering pressure uid from the Working end of said motor to its opposite end in the event of excessive piston speeds, a controlling Valve for yprecluding ow of pressure fluid in said bypass during normal motor operation, and means for permitting passage of fluid through said bypass .in the event of overspeeding of said motor, said pressure iiuid in said bypass oppos- .side of said piston, thereby to provide a cushioning pressure for said piston for automatically checking movement of said piston as it approaches said end of said cylinder.

2l. In combination, an expansible chamber motor including a cylinder containing a reciprocable piston and fluid supply and exhaust means for said cylinder, means automatically responsive to an excessive rate of piston movement during the working stroke of the motor and controlled by the cylinder pressure for supplying pressure fluidv to one end of said cylinder at one side of said piston, thereby to provide a cushioning pressure for said piston for automatically checking movement of said piston as it aproaches said end of said cylinder, said automatic means including means for automatically rendering said cushioning-fluid-supply ineffective during a normal rate of piston movement.

PAUL D. CORNELIUS. 

